JPH11166885A - High-temperature corrosion fatigue testing method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a corrosive environment without arresting high-temperature fatigue testing function by intermittently spraying a corrosive solution to a test piece simultaneously with the induction heating of the test piece, and performing a tensile compression fatigue test. SOLUTION: A corrosive solution spraying device is formed of a corrosive solution tank 5 provided with a compressor 6, and a corrosive solution supplying system 12 connected thereto and having a tip extended to the clearance of an induction coil 1. The corrosive solution supplying system 12 is provided with a solenoid valve 8 connected to a relay type control device 7. The spraying pressure of corrosive solution is obtained by increasing the air pressure within the corrosive solution tank 5 by the compressor 6, and the intermittent spraying is automatically performed by operating the solenoid valve 8 by the relay type control device 7. In spraying, a single surface spraying is performed so that the corrosive solution is not directly touched to a thermocouple 9, whereby the corrosion damage of the thermocouple 9 and the wrong operation of a temperature control device by a sudden temperature change in adhesion of the corrosive solution are prevented. According to this, a high-temperature corrosion fatigue environment can be reproduced in an exhaust system in automobile traveling state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material evaluation test apparatus for reproducing an automobile driving environment in the development of automobile exhaust system materials and a method for evaluating the same.

[0002]

2. Description of the Related Art An automobile exhaust system is a system from an exhaust manifold that collects high-temperature exhaust gas from an engine to a muffler that is released to the atmosphere through a catalytic converter. This system is located under the floor of a car and is exposed to the outside air. The constituent material is required to be able to withstand high temperatures of exhaust gas, vibration or fatigue of the engine or the vehicle body, and corrosion by sea salt particles or snow melting salt.

At present, stainless steel is used for this material. However, since there is no test for reproducing the running environment, that is, there is no material evaluation method for simultaneously reproducing high temperature, fatigue, and corrosion,
Materials are selected based on the results of individual evaluation tests such as salt damage corrosion resistance and high temperature fatigue characteristics. For this reason, materials with excessive characteristics that are added together with multiple elements effective for improving characteristics based on the results of individual tests, and materials with insufficient characteristics due to severe environments that can not be predicted by individual tests are used there is a possibility.

[0004]

In view of the above situation, the inventors of the present invention have proposed that the most suitable stainless steel for the exhaust system can be reproduced as accurately as possible in an automobile driving environment, that is, high temperature, fatigue and corrosion. It was considered necessary to develop a material evaluation method and apparatus that can reproduce the same at the same time.

Conventionally, a high-temperature fatigue tester has been used for a test for simultaneously reproducing high temperature and fatigue, and the inventors have attempted to develop a test device for reproducing a vehicle driving environment by improving this test device. . That is, an object of the present invention is to provide a high-temperature corrosion fatigue test method and a high-temperature corrosion fatigue test method in which a means for reproducing a corrosive environment is incorporated into a conventional high-temperature fatigue device without impairing the function as an original high-temperature fatigue tester. To provide.

[0006]

First, the conventional high temperature fatigue test apparatus can be roughly divided into two types based on the high temperature heating method. One uses a heating furnace, and the other uses an induction coil. The former is a heating method in which the specimen is held in a heating furnace.However, when a corrosive environment is introduced into the furnace, the corrosion liquid may evaporate before adhering to the specimen. But not
The possibility of furnace wall damage arises as a problem. It is very difficult to avoid these problems.

Accordingly, the inventors have studied the modification of a high-temperature fatigue tester using the latter induction coil. as a result,
The configuration as shown in FIG. 1 solves the above-mentioned problem and makes it possible to provide a test method and an apparatus capable of simultaneously reproducing high temperature, fatigue, and corrosion.

That is, the gist of the present invention is as follows. (1) A high-temperature corrosion fatigue test method characterized by performing a tensile-compression fatigue test while intermittently spraying a corrosive liquid onto the test piece while inductively heating the test piece. (2) A means for inductively heating a test piece, a means for intermittently spraying a corrosive solution on the test piece, and a fatigue test means for tension and compression, wherein the test piece is heated intermittently while the test piece is intermittently heated. A high-temperature corrosion fatigue test apparatus for performing a tensile compression fatigue test while spraying a corrosive liquid. (3) The high-temperature corrosion fatigue test apparatus according to (2), wherein the heating means is an induction coil surrounding the test piece, and the corrosive liquid is guided by using a gap between the induction coils.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The high-temperature corrosion fatigue test apparatus of the present invention will be described in more detail with reference to FIG. A test piece 3 is mounted on a fatigue tester 2 provided with an induction coil 1 capable of a high temperature test. A high voltage is applied to the induction coil by the high-frequency power supply 4, and the test piece 3 held in the induction coil 1 generates Joule heat due to an eddy current due to an AC magnetic field generated by a high-voltage AC electric field flowing through the coil. Therefore, only the metal inside the coil is selectively heated, and substances other than the metal outside the coil and inside the coil are not easily heated.

[0010] In such a specimen heating environment, there is little possibility that the corrosive liquid evaporates before adhering to the specimen.
In addition, there is little possibility of damage to the device due to the corrosive liquid. Further, since the induction coil 1 itself is not easily heated, it is possible to spray a corrosive liquid from the gap of the induction coil 1 toward the test piece as shown in FIG.

A method of supplying a corrosive liquid is a method of spraying a corrosive liquid that can intermittently spray a constant amount of a corrosive liquid, assuming a state in which a fixed amount of salt water adheres to an exhaust system in one driving of the automobile. This is performed by providing a device. The corrosive liquid spraying device comprises a corrosive liquid tank 5 having a compressor 6 and a corrosive liquid supply system 12 connected to the tank 5 and having a tip extending into the gap between the induction coils 1. Type control device 7
And an electromagnetic valve 8 connected to the power supply. Preferably, the pressure of the corrosive liquid to be sprayed is obtained by increasing the air pressure in the corrosive liquid tank 5 by the compressor 6, and the intermittent spray is automatically performed by operating the solenoid valve 8 by the relay control device 7. In this way, a fatigue test that generally takes a long time can be performed fully automatically, including spraying of a corrosive liquid.

It is sufficient to spray the etchant only on one side of the test piece. This is equivalent to reproducing that the exhaust system material undergoes salt damage corrosion only on the surface that comes into contact with the outside air. Also,
The single-sided spraying makes it possible to prevent the corrosive liquid from directly hitting the thermocouple 9, thereby preventing the thermocouple 9 from being damaged by corrosion and the temperature control device 10 from malfunctioning due to a rapid temperature change when the corrosive liquid adheres. It becomes possible. If the protective cover 11 is provided, damage to the fatigue tester due to the sprayed corrosive liquid can be prevented to a minimum.

[0013]

EXAMPLE The results of a high-temperature fatigue test were compared for SUS304 steel, which is currently a material representative of a flexible tube for an automobile exhaust system. The test temperature is the exhaust gas temperature 70
At 0 ° C., the conditions of the fatigue test are such that the maximum stress is changed and the frequency 1 is set so that the minimum stress is 0 MPa (no stress load).
A 0 Hz sinusoidal stress was applied to the specimen. The etching solution was a saturated saline solution at room temperature, the spraying time was 0.4 seconds, the spraying interval was 5 minutes, and the amount of one spraying was about 4.7 cc. FIG.
Figure 9 shows the results of the high temperature corrosion fatigue test. The vertical axis indicates the maximum stress, and the horizontal axis indicates the number N of times of stress repetition at the time of fracture. FIG. 2 also shows a cycle test ○ mark and a high temperature fatigue test ● mark as comparative examples.

The cycle test of the comparative example indicated by ○ is a test result that the inventors conducted before the present invention. This is a repetitive test in which a test piece is immersed in a saturated saline solution for 5 minutes, a high-temperature fatigue test for 2 hours, a test piece air-cooled to room temperature, and these are made into one cycle. In this test, high-temperature fatigue and salt damage corrosion cannot always be reproduced at the same time, but the fatigue strength is greatly reduced as compared with the simple high-temperature fatigue test in which the test piece is not immersed in salt water as indicated by ●. This is because in high-temperature fatigue, the effect of salt damage corrosion has a great effect on the reduction in fatigue strength.

In the high temperature corrosion fatigue test of the present invention shown by □,
Furthermore, the fatigue strength has been reduced. This is because extremely severe conditions in which high temperature, fatigue and corrosion act simultaneously, which could not be reproduced conventionally, are reproduced. Accordingly, the test method and apparatus of the present invention allow high-temperature, fatigue, and corrosion to act simultaneously. For example, a high-temperature corrosion-fatigue environment in, for example, an exhaust system in an automobile running state can be reproduced more faithfully, and the selection of a material that can withstand the environment can be more conventionally performed. Now you can do it properly.

[0016]

According to the high temperature corrosion fatigue test apparatus of the present invention,
It becomes possible to reproduce a high-temperature corrosion fatigue environment in an exhaust system or the like in a running state of an automobile. This makes it possible to select a more appropriate automobile exhaust system stainless steel than before, greatly contributing to lower cost and longer life of automobile exhaust system components. Therefore, it can be said that the present invention is an invention having extremely high industrial value.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a high-temperature corrosion fatigue test apparatus according to the present invention.

FIG. 2 is a diagram showing an example of a high temperature corrosion fatigue test according to the present invention and a conventional test method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Induction coil 2 Fatigue test device 3 Test piece 4 High frequency power supply 5 Corrosion liquid tank 6 Compressor 7 Relay type control device 8 Solenoid valve 9 Thermocouple 10 Temperature control device 11 Protective cover 12 Corrosion liquid supply system

Claims (3)

[Claims] 1. A high temperature corrosion fatigue test method comprising: performing a tensile compression fatigue test while intermittently spraying a corrosive liquid onto the test piece while inductively heating the test piece. Means for inductively heating the test piece, means for intermittently spraying a corrosive liquid onto the test piece, and means for fatigue test of tension and compression. A high-temperature corrosion fatigue test apparatus characterized by performing a tensile compression fatigue test while spraying a corrosive liquid. 3. The high-temperature corrosion according to claim 2, wherein the means for induction-heating the test piece is an induction coil surrounding the test piece, and the corrosive liquid is guided by using a gap between the induction coils. Fatigue test equipment.